U.S. Pat. No. 4,365,345 (Craig et al) describes apparatus of this kind, in which, however, the beam source is located beneath the table in the actual patient investigation part of the apparatus, and the image receptor is located on a tower structure arranged above said patient investigation part. When the beam source is moved in the X- and Y-directions these movements are transferred to the receptor over a servo system. In this case, the actual patient investigation part is expansive and space consuming and is found difficult to work with by the X-ray personnel. Another significant drawback with this known apparatus is that there is no possibility of taking side photographs with a horizontally directed beam path.
U.S. Pat. No. 4,024,403 (Bernstein et al) teaches a conventional tower structure with manual adjustment of the patient support table, an overlying beam source and a receptor located beneath the table. The apparatus includes an electrical auxiliary device for adjusting the beam source angle and synchronized movement of the receptor corresponding to said angular adjustment, such that the central beam will always impinge on the patient at the correct angle.
The work required from the X-ray personnel with this type of X-ray equipment is both laborious and complicated, placing great strain on the shoulders and back muscles of the personnel as a result of the manual adjustment movements which must be carried out, not least the displacement of the heavy beam source. This equipment also lacks a facility for taking side photographs with horizontal beam path.
U.S. Pat. No. 4,365,344 (Dornheim) provides an example of apparatus incorporating mechanical synchronization between the setting movements of the receptor and beam source. This arrangement utilizes a complicated lever system, which makes the work carried out by the X-ray personnel both heavy and complicated, primarily because of the large masses which need to be activated, and also because of the stretching and bending required of said personnel. Furthermore, the receptor part of the apparatus must be lifted up each time a side photograph is taken. The possibility of taking angled photographs is limited.
U.S. Pat. No. 3,492,482 (Forsyth) describes and illustrates a beam source which is mounted on a vertical tower structure and which is movable in the Z-direction, and a receptor part which is moved synchronously with the beam source on a corresponding vertical tower structure. The apparatus is intended exclusively for taking side photographs with horizontal beam path, and the apparatus consequently has a limited field of use.
GB-B-1,323,769 (Picket Corp) describes apparatus comprising a receptor part in a patient support table and an overlying ceiling-carried beam source. This apparatus affords the possibility of taking side photographs with horizontal beam path, by swinging-up the patient support table about a horizontal axis and pivoting the beam source. The apparatus also enables the image size and shutter setting to be varied in relation to the beam-source/receptor distance ("SID", i.e. "source-image-distance"). Movement of the beam source and swinging of the patient support table, however, must be effected manually, circumstances which are also experienced as troublesome by the X-ray personnel.
SE-B-7906060-5 (Philips) describes a similar arrangement of apparatus, although in this case the beam source is located in the pivotal patient support table and the image receptor is located on a ceiling-carried frame structure, even though it is stated in the descriptive part of the specification that the arrangement may be reversed. Movements of the receptor and beam source in the X-direction are synchronized. When swinging up the table incorporating the beam source, the receptor is rotated around the horizontal axis synchronously therewith. It is also stated that the receptor and beam source can also moved synchronously in the Y-direction, although this is not illustrated in the specification.
This arrangement of apparatus also has the drawbacks associated with a pivotal patient support table, inter alia because of the large masses which need to be set in motion when taking side photographs, and because of the limited use possibilities of the apparatus in general. For example, there is no facility for taking side photographs of a seated patient. In summary it can be said that all apparatus or equipment of this kind lack the requisite flexibility.
Other examples of known X-ray tower structures are described and illustrated in DE-A1-3,406,717 (Philips), DE-A1-2,831,058 (Philips) and U.S. Pat. No. 4,501,011 (Hauck et al).